Standard immunostains for melanoma in sentinel lymph node specimens: which ones are most useful?

Background: Sentinel lymph node (SLN) biopsy in melanoma is an increasingly used procedure. Pathologic evaluation of SLNs using immunohistochemistry improves diagnostic accuracy, yet no universally accepted standard protocol for pathologic processing of SLNs exists.
Objective: The primary purpose of this study was to evaluate our experience with the sensitivity of the immunostains S-100, HMB-45, and Melan-A for SLN biopsy.
Methods: Ninety-nine positive SLNs from 72 patients were retrospectively reviewed for the presence of microscopic metastatic melanoma on hematoxylin and eosin (H&E), S-100, HMB-45, and Melan-A stained sections and sensitivities of each immunohistochemical stain were determined.
Results: The sensitivities of S-100, HMB-45, and Melan-A were 97%, 75%, and 96% respectively.
Conclusion: Given the lower sensitivity of HMB-45, our practice for evaluation of SLN biopsy specimens was modified using combinations of H&E, S-100, and Melan-A without HMB-45. If the H&E sections are negative or equivocal for metastatic melanoma, immunohistochemistry staining with S-100 protein and Melan-A is performed. New and improved protocols will undoubtedly be forthcoming as the field advances.